Compressor

ABSTRACT

The present invention is to reduce a pressure drop in a compressor caused by a suction throttle valve. A compressor  100  includes: a suction chamber  141 ; a suction passage  104   c  communicating with the suction chamber  141 ; and a suction throttle valve  200  for changing the opening degree of the suction passage  104   c . Here, pressure in a region of the suction chamber  141 , apart from another region of the suction chamber  141  in the neighborhood of the suction throttle valve  200  and lower in pressure, is introduced into the suction throttle valve  200  through a pressure introducing passage  104   g . This increases the pressure difference before and behind the suction throttle valve  200  to make the opening degree larger. As a result, a pressure drop by the suction throttle valve  200  can be reduced to suppress performance degradation due to providing the suction throttle valve  200.

TECHNICAL FIELD

The present invention relates to a compressor including a suction throttle valve for changing the opening degree of a suction passage according to a difference between pressure in a suction chamber and pressure in the suction passage.

BACKGROUND ART

Patent Document 1 discloses a suction throttle valve for changing the opening degree of a refrigerant circuit from the outlet of an evaporator to a compressor suction chamber according to the increase or decrease of a refrigerant flow rate.

When the refrigerant is at a low flow rate, the above suction throttle valve decreases the opening degree of the refrigerant circuit from the outlet of the evaporator to the compressor suction chamber to prevent suction pressure pulsation caused by self-excited vibration of a compressor suction valve from passing through the refrigerant circuit from the outlet of the evaporator to the compressor suction chamber and being transmitted to the evaporator to generate noise.

REFERENCE DOCUMENT LIST Patent Document

-   Patent Document 1: Japanese Patent Application Laid-open Publication     No. 2006-214396

SUMMARY OF THE INVENTION Problems to be Solved by the Invention

However, since the suction throttle valve is structured to operate according to a pressure difference between pressure on the suction passage side (upstream pressure, primary pressure) and pressure on the suction chamber side (downstream pressure, secondary pressure) and to bias a valve element in a valve closing direction by an elastic member (spring), the suction throttle valve causes a pressure drop, and the pressure drop becomes a factor for performance degradation of the refrigerant circuit.

Particularly, in a compressor with a suction chamber arranged annularly, a large pressure distribution occurs in the suction chamber. Since a region in the neighborhood of the suction throttle valve inside the suction chamber is a connection region with the suction passage, the region is a region with pressure higher than the other regions in the suction chamber. The valve element of the conventional suction throttle valve operates in response to the highest pressure in this suction chamber, and this becomes a factor for increasing the pressure drop.

Therefore, it is an object of the present invention to provide a compressor capable of reducing a pressure drop caused by a suction throttle valve.

Means for Solving the Problems

In order to attain the above object, a compressor according to the present invention includes: a suction chamber annularly formed around a drive shaft; a suction passage communicating with the suction chamber, and a suction throttle valve for changing the opening degree of the suction passage according to a pressure difference between pressure in the suction chamber and pressure in the suction passage, wherein pressure in a region of the suction chamber, apart from another region of the suction chamber in the neighborhood of the suction throttle valve and lower in pressure, is introduced into the suction throttle valve through a pressure introducing passage.

Effects of the Invention

According to the compressor of the present invention, since pressure lower than that in the neighborhood of the suction throttle valve is introduced as pressure in the suction chamber that acts on the suction throttle valve to close the valve, a pressure drop caused by the suction throttle valve can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of a compressor according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a suction throttle valve in FIG. 1.

FIG. 3 is a view illustrating the structure of a cylinder head illustrated in FIG. 1.

FIG. 4 is a sectional view illustrating the structure of the suction throttle valve according to the embodiment of the present invention.

FIG. 5 is a view illustrating a pressure introducing passage according to another embodiment of the present invention.

FIG. 6 is a sectional view illustrating a mounting portion of a suction throttle valve according to the other embodiment of the present invention.

MODES FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

FIGS. 1 to 3 illustrate a variable displacement compressor 100 as an example of a compressor.

The variable displacement compressor 100 includes a cylinder block 101 with multiple cylinder bores 101 a formed therein, a front housing 102 provided at one end of the cylinder block 101, and a cylinder head 104 provided at the other end of the cylinder block 101 through a valve plate 103.

A drive shaft 110 is provided across the inside of a crank chamber 140 formed by the cylinder block 101 and the front housing 102.

A swash plate 111 is arranged around the middle part of the drive shaft 110 in the axial direction thereof.

The swash plate 111 is coupled to a rotor 112 fixed to the drive shaft 110 through a link mechanism 120 to be able to change its inclination relative to the drive shaft 110.

The link mechanism 120 includes a first arm 112 a provided to protrude from the rotor 112, a second arm 111 a provided to protrude from the swash plate 111, and a link arm 121 with one end pivotably coupled to the first arm 112 a through a first coupling pin 122 and the other end pivotably coupled to the second arm 111 a through a second coupling pin 123.

A through hole 111 b of the swash plate 111 is formed into a shape that allows the swash plate 111 to be able to move in an inclined manner in a range between the maximum inclination (θ max) and the minimum inclination (θ min), and a minimum inclination restricting part that comes into contact with the drive shaft 110 is formed in the through hole 111 b.

In the case where the inclination of the swash plate 111 when the swash plate 111 intersects with the drive shaft 110 at right angles is set to 0 deg, the minimum inclination restricting part of the through hole 111 b is so formed that the inclination of the swash plate 111 can be displaced approximately up to 0 deg.

An inclination-decreasing spring 114 for biasing the swash plate 111 toward the minimum inclination is placed between the rotor 112 and the swash plate 111, and an inclination-increasing spring 115 for biasing the swash plate 111 in a direction to increase the inclination of the swash plate 111 is placed between the swash plate 111 and a spring supporting member 116 provided on the drive shaft 110.

Here, the biasing force of the inclination-increasing spring 115 at the minimum inclination is set larger than the biasing force of the inclination-decreasing spring 114, and when the drive shaft 110 is not rotated, the swash plate 111 is located at such an inclination that the biasing force of the inclination-decreasing spring 114 and the biasing force of the inclination-increasing spring 115 are balanced.

One end of the drive shaft 110 passes through the inside of a boss part 102 a of the front housing 102 and extends up to the outside of the front housing 102 to be coupled to a power transmission device, not illustrated.

Note that a shaft seal device 130 is inserted between the drive shaft 110 and the boss part 102 a to disconnect the inside of the crank chamber 140 from the external space.

The drive shaft 110 and the rotor 112 are supported by shaft bearings 131, 132 in the radial direction, and supported by a shaft bearing 133 and a thrust plate 134 in a thrust direction. Note that a gap between a portion of the drive shaft 110, which comes into contact with the thrust plate 134, and the thrust plate 134 is adjusted by an adjusting screw 135 to a predetermined gap.

Then, power from an external drive source is transmitted to the power transmission device so that the drive shaft 110 will rotate in synchronization with the power transmission device.

A piston 136 is arranged in each of the cylinder bores 101 a, an outer peripheral part of the swash plate 111 is housed in an internal space of an end part of the piston 136 that protrudes on the side of the crank chamber 140 so that the swash plate 111 will move in conjunction with the piston 136 through a pair of shoes 137. Therefore, the piston 136 reciprocates in the cylinder bore 101 a along with the rotation of the swash plate 111.

In the cylinder head 104, a discharge chamber 142 defined in a central portion by an annular partition wall 104 a, and a suction chamber 141 defined by the partition wall 104 a and an outer peripheral wall 104 b to surround the discharge chamber 142 annularly are formed.

The suction chamber 141 communicates with the cylinder bores 101 a through suction holes 103 a and a suction valve (not illustrated) provided in the valve plate 103, and the discharge chamber 142 communicates with the cylinder bores 101 a through discharge holes 103 b and a discharge valve (not illustrated) provided in the valve plate 103.

The front housing 102, a center gasket (not illustrated), the cylinder block 101, a cylinder gasket (not illustrated), the valve plate 103, a head gasket (not illustrated), the cylinder head 104, and the like mentioned above are fastened by multiple through bolts 105 to form a compressor housing.

A suction passage 104 c for causing a refrigerant circuit on the low-pressure side of a refrigeration system (for example, a vehicle air conditioning system) and the suction chamber 141 to communicate with each other is formed in the cylinder head 104, and this results in connecting the suction chamber 141 to the refrigerant circuit on the low-pressure side of the refrigeration system.

The suction passage 104 c is provided to extend from the outside of the cylinder head 104 (drive shaft 110) toward the suction chamber 141 along the radial direction of the drive shaft 110.

The suction passage 104 c is composed of a suction port 104 c 1 to which the low-pressure side refrigerant circuit is connected, and a communication hole 104 c 2 through which the suction port 104 c 1 and the suction chamber 141 are connected, and a suction throttle valve 200 is arranged between the communication hole 104 c 2 and the suction chamber 141.

The suction throttle valve 200 operates according to a pressure difference between the suction passage 104 c (upstream side) and the suction chamber 141 (downstream side), and when the pressure difference is less than or equal to a predetermined value, i.e., when the refrigerant flow rate is low, the opening area (opening degree) of the suction passage 104 c is decreased to the minimum to increase the refrigerant flow rate, while when the pressure difference increases in excess of the predetermined value, the opening area (opening degree) of the suction passage 104 c is increased.

Then, the suction throttle valve 200 decreases the opening degree of the suction passage 104 c in a region with a low refrigerant flow rate to suppress the pressure pulsation of the suction chamber 141 from being transmitted to an evaporator through the low-pressure side refrigerant circuit.

Further, the discharge chamber 142 is connected to a discharge-side external refrigerant circuit of the refrigeration system through a discharge passage 104 d. The discharge passage 104 d is provided to extend from the outside of the cylinder head 104 toward the inside of the radial direction of the drive shaft 110 so as to communicate with the discharge chamber 142 across the suction chamber 141.

A control valve 300 is further provided in the cylinder head 104.

The control valve 300 adjusts the opening degree of a communication passage 145 for causing the discharge chamber 142 and the crank chamber 140 to communicate with each other to control the introduction amount of discharged gas into the crank chamber 140.

The refrigerant in the crank chamber 140 flows into the suction chamber 141 via a communication passage 146 formed by an orifice 103 c formed in a communication passage 101 b, a space 101 c, and the valve plate 103.

Thus, pressure in the crank chamber 140 can be changed by the control valve 300 to change the inclination angle of the swash plate 111, i.e., the stroke of the piston 136 in order to perform variable control of the discharge amount of the variable displacement compressor 100.

At the operating time of the refrigeration system, i.e., in the state of operating the variable displacement compressor 100, the energization amount of a solenoid built in the control valve 300 is adjusted in response to an external signal to variably control the discharge amount so that pressure in the suction chamber 141 introduced into the control valve 300 through a communication passage 104 e will be a predetermined value.

Referring to FIGS. 2 to 4, the structure of the suction throttle valve 200 will be described in detail below.

The suction throttle valve 200 is composed of a cylindrical first housing 201, a bottomed cylindrical second housing 204, a bottomed cylindrical valve element 202, and a compression coil spring 203.

An inlet hole 201 a, a valve seat 201 b, and a flange 201 c are formed in the first housing 201.

The second housing 204 has a cylindrical space 204 a for housing the valve element 202 and the compression coil spring 203. In the cylindrical surface of the second housing 204, each of multiple outlet holes 204 b formed nearly into a pentagon shape having a vertex angle toward the side of the valve seat 201 b is formed with an end side 204 c fixedly fitted in the outer circumference of the inlet hole 201 a of the first housing 201.

The valve element 202 is housed in the second housing 204 in a manner to be able to move in the space 204 a in the axial direction, and the compression coil spring 203 is provided in a compressed state between the bottom side of the internal space of the valve element 202 and the bottom side of the second housing 204 so that the compression coil spring 203 will bias the valve element 202 in a direction to be seated in the valve seat 201 b, i.e., toward the valve closing direction.

An annular recessed portion is formed on the inner peripheral face of one end side 204 c of the second housing, a corresponding annular protruded portion is formed on the outer peripheral face of the first housing 201, and both are fitted to fix the second housing 204 to the first housing 201.

Note that the first housing 201, the second housing 204, and the valve element 202 are resin molded products.

Further, an annular protruded portion is formed on the outer peripheral face of the flange 201 c of the first housing 201 as one end side of the suction throttle valve 200, and this annular protruded portion is fitted in an annular recessed portion formed in the communication hole 104 c 2 of the suction passage 104 c so that the suction throttle valve 200 will be positioned and retained inside the suction passage 104 c.

The suction throttle valve 200 is arranged in an extended region of the suction passage 104 c so that the outlet hole 204 b will face the inside of the suction chamber 141.

The valve element 202 has one end face 202 a that comes into contact with the valve seat 201 b and a cylindrical outer peripheral face 202 b, and is slidably supported by the cylindrical inner peripheral face of the second housing 204 to divide the cylindrical space 204 a into a first space 204 a 1, which causes the suction passage 104 c and the suction chamber 141 to communicate with each other, and a second space 204 a 2.

Then, the valve element 202 moves inside the second housing 204 in the axial direction to change the opening area of the outlet hole 204 b, i.e., the opening area (opening degree) of the suction passage 104 c.

Note that a groove 201 d having a predetermined width is formed as a recessed portion in part of the valve seat 201 b of the first housing 201, and an apex angle portion of the outlet hole 204 b communicates with the internal space of the groove 201 d.

Therefore, when one end face 202 a of the valve element 202 is seated in the valve seat 201 b, the suction passage 104 c is not completely blocked and the suction passage 104 c communicates with the suction chamber 141 through the inlet hole 201 a, the groove 201 d, and the apex angle portion of the outlet hole 204 b.

The opening area of the apex angle portion of the outlet hole 204 b when one end face 202 a of the valve element 202 is seated in the valve seat 201 b is smaller than the flow passage area of the groove 201 d, and the opening area of the apex angle portion of the outlet hole 204 b at this time becomes the minimum opening area (smallest opening degree).

The minimum opening area is set as an area capable of preventing self-excited vibration of the valve element 202 in a region with a very low refrigerant flow rate, but in consideration of vacuuming of the inside of the variable displacement compressor 100 before being filled with the refrigerant, the minimum opening area is set to a value larger at least than the opening area of the orifice 103 c.

Further, a communication hole 204 d is formed in the bottom wall of the second housing 204, and the communication hole 204 d causes the second space 204 a 2, defined by the second housing 204 and the valve element 202, and the suction chamber 141 to communicate with each other.

The bottom of the second housing 204 of the suction throttle valve 200 is housed in a recessed part 104 f, which forms the partition wall 104 a as a recessed part on the side of the discharge chamber 142 to define the discharge chamber 142 and the suction chamber 141 located in an extended region of the suction passage 104 c.

Then, the inside of the recessed part 104 f communicates, through a pressure introducing passage 104 g formed across the discharge chamber 142, with a region (region A in FIG. 3) of the suction chamber 141 on a side opposite, across the discharge chamber 142, to a region of the suction chamber 141 with the suction throttle valve 200 provided.

The pressure introducing passage 104 g is formed in an extended region of the suction passage 104 c, i.e., linearly along the radial direction of the drive shaft 110, and the opening end thereof on the bottom wall side of the recessed part 104 f is arranged to face the communication hole 204 d.

Here, the cross-section area of a gap 150 between the outer peripheral face of the second housing 204 and the inner peripheral face of the recessed part 104 f is set smaller than the minimum cross-section area of the communication hole 104 g, and the gap 150 defines a connection region between the communication hole 204 d in the recessed part 104 f and the pressure introducing passage 104 g, and a region (region B in FIG. 3) in the suction chamber 141 in the neighborhood of the outlet hole 204 b of the suction throttle valve 200.

Thus, pressure in the region A of the suction chamber 141 facing the second space 204 a 2 across the shaft center of the drive shaft 110 acts on the second space 204 a 2 via the pressure introducing passage 104 g, the recessed part 104 f, and the communication hole 204 d.

Note that a seal member such as an O-ring can be arranged in the gap 150, and providing the seal member can cause the pressure in the region A of the suction chamber 141 to act on the second space 204 a 2 more securely.

As mentioned above, pressure in the suction passage 104 c is introduced into the upstream side of the valve element 202, pressure in the region A of the suction chamber 141 is introduced into the downstream side of the valve element 202, and the suction throttle valve 200 adjusts the opening degree of the suction passage 104 c by following a difference between these pressures, i.e., a change in refrigerant circulating amount.

The pressure difference at which the valve element 202 operates is determined based on the pressure receiving area of the valve element 202 and the biasing force of the compression coil spring 203. For example, the pressure receiving area of the valve element 202 and the biasing force of the compression coil spring 203 are so set that the valve will operate to open with a minute pressure difference around 100 kPa.

In the refrigeration system including the variable displacement compressor 100 provided with the above-mentioned suction throttle valve 200, when the variable displacement compressor 100 operates to circulate the refrigerant through the refrigerant circuit, the suction throttle valve 200 adjusts the opening degree of the suction passage 104 c by following the refrigerant circulating amount in such a manner to increase the opening degree of the suction passage 104 c as the refrigerant circulating amount increases, or to decrease the opening degree of the suction passage 104 c as the refrigerant circulating amount decreases.

For example, when the refrigeration system is a vehicle air conditioning system, the refrigerant circulating amount increases under such conditions, so-called high-load conditions, that the vehicle thermal load is high. When the suction chamber 141 is annularly formed, a pressure distribution occurs in the suction chamber 141, but since a region (region B in FIG. 3) in the suction chamber 141 in the neighborhood of the suction throttle valve 200 is the connection region with the suction passage 104 c, the region is located upstream of the other regions in the suction chamber 141, which is the region with the highest pressure in the suction chamber 141.

However, the pressure in the suction chamber 141 that acts on the valve element 202 of the suction throttle valve 200 is the pressure in the region A, and since the region A is located on the downstream side apart from the region B with the highest pressure, the pressure in the region A is lower than that in the region B.

Therefore, the pressure difference before and behind the valve element 202 of the suction throttle valve 200, where the pressure in the region A of the suction chamber 141 acts on the valve element 202, becomes larger than that of a suction throttle valve where the pressure in the region B of the suction chamber 141 acts on a valve element thereof, resulting in a larger opening degree. As a result, a pressure drop by the suction throttle valve 200 can be reduced to suppress performance degradation due to providing the suction throttle valve 200.

In the example illustrated in FIG. 3, the region B of the suction chamber 141 in which the suction throttle valve 200 is provided is such that the pressure introducing passage 104 g is connected to the region A facing the region B across the shaft center of the drive shaft 110 to introduce the pressure in the region A into the suction throttle valve 200 as the pressure in the suction chamber 141, but the region to which the pressure introducing passage 104 g is connected is not limited to the region A, and it can be any other region apart from the region B of the suction chamber 141 with the suction throttle valve 200 provided and lower in pressure than the region B.

Note that the region of the suction chamber 141 to which the pressure introducing passage 104 g is open can be a region in which pressure becomes lower than or equal to the pressure in the region B by a predetermined pressure (e.g., 100 kPa) under the high-load conditions, especially a region with the lowest pressure in the suction chamber 141, to enhance the effect of reducing the pressure drop.

Thus, the pressure introducing passage 104 g is not limited to the structure formed linearly in the radial direction of the drive shaft 110, and it can be a structure having a bending portion along the path.

However, in the compressor 100 with the suction chamber 141 annularly formed and the discharge chamber 142 arranged inside thereof, the pressure introducing passage 104 g can be provided integrally with the cylinder head 104 to extend across the discharge chamber 142 in projection in the axial direction of the drive shaft 110 as mentioned above to introduce pressure in a region, apart from the region B and lower in pressure, into the suction throttle valve 200 at short distance without enlarging the outer diameter of the cylinder head 104.

When the cross-section area of the annular suction chamber 141 is substantially uniform, since pressure near a region facing the region B of the suction chamber 141 in which the suction throttle valve 200 is provided, i.e., pressure in the region A farthest from the region B becomes the lowest, the pressure introducing passage 104 g is connected to the region A in the example illustrated in FIG. 3.

In the above-mentioned suction throttle valve 200, the opening degree under the high-load conditions becomes larger than that of a suction throttle valve operating based on the pressure in the region B, and the effect of reducing the pressure pulsation is on a declining trend. However, in the case of the vehicle air conditioning system, the pressure pulsation level in the suction chamber 141 that becomes evident as vehicle interior noise under the high-load conditions is low, which substantially causes no problem.

Further, the refrigerant circulating amount decreases as the thermal load becomes smaller, and as a result, the pressure distribution (variation in pressure) in the suction chamber 141 becomes small. Therefore, the pressure in the region A comes close to the pressure in the region B, and the opening degree of the suction throttle valve 200 comes close to that in the case of operating according to the pressure in the region B.

Since the pressure pulsation level in the suction chamber 141 is on an increasing trend under such low-load conditions that the refrigerant circulating amount decreases, the effect of reducing the pressure pulsation nearly equal to that in the case of operating according to the pressure in the region B can be obtained under the low-load conditions with the effect of reducing the pressure pulsation required.

In other words, since the suction throttle valve 200 is so structured that, when a pressure distribution occurs in the suction chamber 141, pressure in a region lower in pressure acts on the valve element 202, performance degradation can be suppressed by placing the suction throttle valve 200 without impairing the effect of reducing vehicle interior noise caused by the suction pressure pulsation, especially under such high thermal load conditions that the refrigerant circulating amount increases.

In the meantime, when the discharge passage 104 d crosses the suction chamber 141 so that the cross-section area of a flow passage of the suction chamber 141 will be extremely narrowed by the discharge passage 104 d to form a narrowed portion, a region with the lowest pressure in the suction chamber 141 may be a region AA illustrated in FIG. 5, rather than the region A facing the region B of the suction chamber 141 with the suction throttle valve 200 provided, i.e., the region AA on the farther side from the region B of the suction chamber 141 in the neighborhood of the suction throttle valve 200 between regions AA and BB that face each other across the narrowed portion of the suction chamber 141 may be the region with the lowest pressure in the suction chamber 141.

In such a case, a pressure introducing passage 104 g 2 provided to extend from the region AA in the radial direction of the cylinder head 104 can be formed toward a pressure introducing passage 104 g 1 formed in an extended region of the suction passage 104 c from the region B to cause the pressure introducing passage 104 g 1 and the pressure introducing passage 104 g 2 to communicate with each other in order to introduce the pressure in the region AA into the suction throttle valve 200.

Here, since the pressure introducing passage 104 g 1 that communicates with the communication hole 204 d of the second housing 204 is the extended region of the suction passage 104 c, i.e., the pressure introducing passage 104 g 1 is provided to extend up to a region near the center of the radial direction along the radial direction of the cylinder head 104 (drive shaft 110), even if a region apart from the region B and lower in pressure is located at any angular position, the pressure introducing passage 104 g 2 can be provided to extend from the region in the radial direction to form the pressure introducing passage 104 g.

While the content of the present invention has been specifically described with reference to the preferred embodiment, it will be obvious that a person skilled in the art can contemplate various variations based on the basic technical idea and teaching of the present invention.

In the example illustrated in FIG. 2, although the gap 150 defines the connection region between the communication hole 204 d in the recessed part 104 f and the pressure introducing passage 104 g, and the region (region B in FIG. 3) inside the suction chamber 141 in the neighborhood of the outlet hole 204 b of the suction throttle valve 200, the regions can be defined by an annular gap 160 between the bottom of the second housing 204 and the bottom wall of the recessed part 104 f as illustrated in FIG. 6. Here, a seal member such as an O-ring can be arranged in the annular gap 160.

Further, the bottom of the second housing 204 and the bottom wall of the recessed part 104 f can be structured to come into contact with each other so that the annular contacting portion will define the connection region between the communication hole 204 d in the recessed part 104 f and the pressure introducing passage 104 g, and the region (region B in FIG. 3) inside the suction chamber 141 in the neighborhood of the outlet hole 204 b of the suction throttle valve 200. In this case, the contacting portion also functions to position the suction throttle valve 200.

Further, the other end side of the suction throttle valve 200 (the bottom wall side of the second housing 204) is not limited to the structure housed in the recessed part 104 f. For example, a plane corresponding to the bottom wall of the second housing 204 can be formed integrally with the partition wall 104 a for forming a partition between the discharge chamber 142 and the suction chamber 141 to use a gap between this plane and the bottom wall of the second housing 204 as partitioning means.

Further, the axis line of the suction passage 104 c can be set to be located in a plane orthogonal to the shaft line of the drive shaft 110 from the outside of the radial direction of the cylinder head 104 toward the suction chamber 141. In addition to that, the axis line of the suction passage 104 c can be set to be inclined with respect to the plane orthogonal to the shaft line of the drive shaft 110.

Although the suction throttle valve 200 does not block the suction passage 104 c completely when one end face 202 a of the valve element 202 is seated in the valve seat 201 b, a structure for fully closing the suction passage 104 c can also be adopted.

Further, the communication hole 204 d can be formed in the bottom wall of the second housing 204. In addition to that, the communication hole 204 d can be formed in a cylindrical face near the bottom wall of the second housing 204.

The compressor 100 can be a swash-plate type variable displacement compressor. In addition to that, it can also be a wobble-plate type variable displacement compressor. Further, the present invention can be applied to various known compressors, such as a variable displacement compressor with an electromagnetic clutch, a clutchless compressor without an electromagnetic clutch, a fixed displacement type reciprocating compressor, and a motor-driven reciprocating compressor.

REFERENCE SYMBOL LIST

-   100 variable displacement compressor -   101 cylinder block -   102 front housing -   104 cylinder head -   104 c suction passage -   104 g pressure introducing passage -   110 drive shaft -   141 suction chamber -   142 discharge chamber -   200 suction throttle valve -   201 first housing -   204 second housing -   202 valve element -   203 compression coil spring. 

1. A compressor comprising: a suction chamber annularly formed around axis of a drive shaft; a suction passage communicating with the suction chamber; and a suction throttle valve for changing an opening degree of the suction passage according to a pressure difference between pressure in the suction chamber and pressure in the suction passage, wherein pressure in a region of the suction chamber, apart from another region of the suction chamber in the neighborhood of the suction throttle valve and lower in pressure, is introduced into the suction throttle valve through a pressure introducing passage.
 2. The compressor according to claim 1, further comprising a discharge chamber surrounded by the suction chamber, wherein the pressure introducing passage is provided to extend across the discharge chamber in projection in an axial direction of the drive shaft.
 3. The compressor according to claim 1, wherein the pressure introducing passage guides, to the suction throttle valve, pressure in a region of the suction chamber that faces the region of the suction chamber in the neighborhood of the suction throttle valve across axis of the drive shaft.
 4. The compressor according to claim 1, wherein the suction chamber has a narrowed portion in which a cross-section area of a flow passage is partially narrowed, and the pressure introducing passage guides, to the suction throttle valve, pressure in a region on a farther side from the region of the suction chamber in the neighborhood of the suction throttle valve between regions across the narrowed portion of the suction chamber.
 5. The compressor according to claim 4, further comprising a discharge chamber surrounded by the suction chamber, wherein a discharge passage communicating with the discharge chamber is provided across the suction chamber along a radial direction of the drive shaft, and the narrowed portion is formed by the discharge passage.
 6. The compressor according to claim 1, wherein the suction passage is provided in a region outside of the annular suction chamber to extend in the radial direction of the drive shaft, the suction throttle valve includes a valve element and a valve housing for housing the valve element displaceably in the radial direction of the drive shaft, and the pressure introducing passage communicates with an inner end of the valve housing in the radial direction of the drive shaft.
 7. The compressor according to claim 6, wherein in the valve housing, an inlet hole communicating with the suction passage is formed at an outer end in the radial direction of the drive shaft, an outlet hole communicating with the suction chamber is formed in an intermediate peripheral wall, and a communication hole communicating with the pressure introducing passage is formed at the inner end in the radial direction of the drive shaft, and the valve element is displaced in the radial direction of the drive shaft to change an opening area of the outlet hole according to a pressure difference between pressure in the suction chamber introduced into the valve housing through the communication hole and pressure in the suction passage introduced into the valve housing through the inlet hole.
 8. The compressor according to claim 2, wherein the pressure introducing passage guides, to the suction throttle valve, pressure in a region of the suction chamber that faces the region of the suction chamber in the neighborhood of the suction throttle valve across axis of the drive shaft.
 9. The compressor according to claim 2, wherein the suction chamber has a narrowed portion in which a cross-section area of a flow passage is partially narrowed, and the pressure introducing passage guides, to the suction throttle valve, pressure in a region on a farther side from the region of the suction chamber in the neighborhood of the suction throttle valve between regions across the narrowed portion of the suction chamber.
 10. The compressor according to claim 9, further comprising a discharge chamber surrounded by the suction chamber, wherein a discharge passage communicating with the discharge chamber is provided across the suction chamber along a radial direction of the drive shaft, and the narrowed portion is formed by the discharge passage.
 11. The compressor according to claim 2, wherein the suction passage is provided in a region outside of the annular suction chamber to extend in the radial direction of the drive shaft, the suction throttle valve includes a valve element and a valve housing for housing the valve element displaceably in the radial direction of the drive shaft, and the pressure introducing passage communicates with an inner end of the valve housing in the radial direction of the drive shaft.
 12. The compressor according to claim 5, wherein the suction passage is provided in a region outside of the annular suction chamber to extend in the radial direction of the drive shaft, the suction throttle valve includes a valve element and a valve housing for housing the valve element displaceably in the radial direction of the drive shaft, and the pressure introducing passage communicates with an inner end of the valve housing in the radial direction of the drive shaft. 